Auxiliary device for three air flow path gas turbine engine

ABSTRACT

A gas turbine engine has a fan rotor including at least one stage, with the at least one stage delivering a portion of air into a low pressure duct, and another portion of air into a compressor. The compressor is driven by a turbine rotor, and the fan rotor is driven by a fan drive turbine. A channel selectively communicates air from the low pressure duct across a boost compressor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/458,619, filed Aug. 13, 2014, now U.S. Pat. No. 10,400,709 grantedSep. 3, 2019, which claims priority to U.S. Provisional Application No.61/880,207, filed Sep. 20, 2013.

BACKGROUND

This application relates to a gas turbine engine having a lower pressureair flow path selectively driven across a boost compressor.

Gas turbine engines are known and include a fan delivering air into abypass duct and into a core engine compressor. The bypass duct air flowpath is utilized as propulsion and the core air flow path in thecompressor is compressed, mixed with fuel in a combustor, and ignited.Products of this combustion pass downstream over turbine rotors, drivingthem to rotate.

In some applications and, in particular, in military applications, theability to provide adaptive performance including the generation of veryhigh thrust in a very short period of time is desirable. In one proposedengine of this type, a secondary mid-fan supplied third air flow path isprovided, which is at a lower pressure than the fan discharge suppliedprimary bypass air flow path.

This third air flow path may be utilized for various lower pressureapplications, such as cooling. However, this third air flow path is at arelatively low pressure, particularly when compared to the pressure inan exhaust nozzle. As such, downstream uses for this third air flow pathare limited.

SUMMARY

In a featured embodiment, a gas turbine engine has a fan rotor includingat least one stage, with the at least one stage delivering a portion ofair into a low pressure duct, and another portion of air into acompressor. The compressor is driven by a turbine rotor, and the fanrotor is driven by a fan drive turbine. A channel selectivelycommunicates air from the low pressure duct across a boost compressor.

In another embodiment according to the previous embodiment, the fanrotor includes at least two stages, with an upstream fan stagedelivering a portion of air into the low pressure duct, and anotherportion across a downstream fan stage. Air passed downstream of thedownstream fan stage is delivered into the compressor and into a bypassduct.

In another embodiment according to any of the previous embodiments, thefan rotor drives at least three stages, with the first stage fan beingthe upstream fan stage, and a third stage fan being the downstream fanstage. The second stage fan is intermediate the first and the thirdstage fan.

In another embodiment according to any of the previous embodiments, thelow pressure duct is a bypass duct.

In another embodiment according to any of the previous embodiments, airdownstream of the boost compressor is utilized as cooling air.

In another embodiment according to any of the previous embodiments, airdownstream of the boost compressor is delivered into an exhaust gasdownstream of the fan drive turbine.

In another embodiment according to any of the previous embodiments, anaugmentor section is positioned adjacent an exhaust nozzle and air fromthe boost compressor is directed towards the augmentor section.

In another embodiment according to any of the previous embodiments, avalve selectively blocks or allows flow through the low pressure duct toan outlet. When the valve is blocking flow, more air is moved into thechannel and across the boost compressor.

In another embodiment according to any of the previous embodiments, theboost compressor is driven by the fan drive turbine.

In another embodiment according to any of the previous embodiments, agear box is positioned between the fan drive turbine and the boostcompressor, with the gear box affecting a speed change between the fandrive turbine and the boost compressor.

In another embodiment according to any of the previous embodiments, aconnection between the gear box and the boost compressor is a flexibleconnection.

In another embodiment according to any of the previous embodiments, aclutch selectively connects or disconnects drive from the gear box toand the boost compressor.

In another embodiment according to any of the previous embodiments, theclutch is moved to connect drive from the gear box to the boostcompressor when the valve blocks flow through the low pressure duct tothe outlet. The clutch disconnects drive from the gear box to the boostcompressor when the valve allows flow from the low pressure duct to theoutlet.

In another embodiment according to any of the previous embodiments, anexhaust cone positioned downstream of the boost compressor is movable tochange a flow cross-sectional area downstream of the boost compressor.

In another embodiment according to any of the previous embodiments, thechannel passes through a turbine exhaust case strut.

In another embodiment according to any of the previous embodiments, agear box is positioned between the fan drive turbine and the boostcompressor, with the gear box affecting a speed change between the fandrive turbine and the boost compressor

In another embodiment according to any of the previous embodiments, aclutch selectively connects or disconnects drive from the gear box tothe boost compressor.

In another embodiment according to any of the previous embodiments, aclutch selectively connects or disconnects drive from the fan driveturbine to the boost compressor.

In another embodiment according to any of the previous embodiments, anexit cone positioned downstream of the boost compressor is movable tochange a downstream flow cross-sectional area for the boost compressor.

In another embodiment according to any of the previous embodiments, airdownstream of the boost compressor is delivered into an exhaust gas flowdownstream of the fan drive turbine.

These and other features may be best understood from the followingdrawings and specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows an engine in a first position.

FIG. 1B shows the engine in a second position.

FIG. 2A shows a second embodiment in a first position.

FIG. 2B shows the second embodiment in a second position.

FIG. 3 shows a third embodiment.

FIG. 4 shows yet another feature.

DETAILED DESCRIPTION

An engine 20 includes a first stage fan 22, and a second stage fan 24. Afan rotor 19 drives the first stage and second stage fans 22 and 24, andalso drives a third stage fan 28. The fan rotor 19 is driven to rotateby a fan drive turbine 40.

A portion of the air downstream of the second stage fan 24 is deliveredinto a duct 26 as low pressure, low temperature intermediate flow. Thisis known as a “third air flow path (C).”

A portion of air from the second stage fan 24 is also delivered acrossthe third stage fan 28. The air passing into duct 26 does not pass overthird stage fan 28, which is received within a housing 29. A portion ofthe air downstream of the third stage fan 28 is delivered as a bypassair flow path (“B”) into a duct 30, and exits at a downstream end 31 asair for cooling and propulsion. A variable nozzle 17 may also beincluded at downstream end 31.

Another portion of the air downstream of the third stage fan 28 isdelivered into a core air flow path (“A”) at duct 34 and passes across acompressor 32. The compressor 32 compresses the air and delivers it intoa combustor 36 where it is mixed with fuel and ignited.

Downstream of the combustor 36, the air crosses a turbine rotor 38,which drives the compressor 32. Downstream of the turbine rotor 38, theair passes across the fan drive turbine 40. An exhaust cone 42 is shownnear a downstream end 31 and within an exhaust duct 13. A variablenozzle 17 is downstream of exhaust duct 13.

As shown in FIG. 1A, air from the duct 26 may be selectively broughtthrough a plurality of channels 48 (only one of which is shown), whichare formed within a turbine exhaust case strut 179. The air from thechannels 48 passes across a boost compressor 46, which is also driven bythe fan drive turbine 40 through a linkage 44. This then raises thepressure of the air in the third air flow path such that when it exitsat outlet 50, it is at a high enough pressure that it may move into aflow of exhaust gas 101. Alternatively, the air from exit 50 may betapped in whole or in part to a use 400, shown schematically, such as acooling use. As is clear from the Figures the air passing through thechannels 48 moves radially inwardly of duct 26, and radially inwardly ofthe core air flow A. When the air C exits through outlet 50, it isradially inward of the core air flow A downstream of the fan driveturbine 40.

A valve 60 is in an open position in FIG. 1A and the flow of air would,thus, generally pass to an outlet 61, as the third air flow pathpropulsion. A smaller volume of air may actually pass into channels 48and to the boost compressor 46 in this open position.

However, as shown in FIG. 1B, the valve 60 is moved to a closed positionto block flow through the duct 26 and a higher portion of the third airflow path in duct 26 passes into channels 48 and across the boostcompressor 46 and to the outlet 50. Now, there is additional air withinthe variable nozzle 17 as propulsion air.

The size of the letter C is shown large and small in the Figures toillustrate the relative volumes of air flow in the two positions.

In addition, an augmentor 99 may be positioned adjacent downstream end31. Augmentor 99 is shown schematically, but, as known, provides a finalburn by mixing additional fuel into the exhaust gas 101. The third airflow path from the duct 26 will have a higher oxygen content than wouldthe air in exhaust gas 101 otherwise downstream of the fan drive turbine40, since the gases passing across fan drive turbine 40 have beencombusted. Thus, the air from duct 26 passing across boost compressor 46and out of outlet 50 to be directed towards the augmentor will increasethe efficiency of the augmentor function.

A control 800 controls the position of valve 60 to achieve the desireduse of the third air flow path. As can be appreciated, air directed intochannel 48 passes across the boost compressor 46 and is mixed with theairflow A which has passed through the combustor 36, and across the fandrive turbine 40. Air which continues to the outlet 61 of the duct 26exits at the outlet 61 downstream of the augmentor 99.

FIG. 2A shows an open position for a second embodiment 700. Inembodiment 700, a gear box 200 is connected through a linkage 202 to bedriven by the fan drive turbine 40. The gear box is connected by aflexible coupling 102 to a clutch 100. Clutch 100 selectively drives aboost compressor 46. A control 800, shown schematically, selectivelyoperates the clutch 100 in combination of the control of the valve 600,as shown in FIGS. 2A and 2B, such that air flow may be directed almostentirely through the duct 26, or almost entirely across the boostcompressor 46.

When the clutch 100 is disconnected, as shown in FIG. 2A, then the airflow is not driven across the boost compressor 46. Instead, the air flowwill largely pass toward the outlet 61. On the other hand, when theclutch 100 is connected, as shown in FIG. 2B, it does drive the boostcompressor 46, which will draw the majority of air flow across the boostcompressor 46.

Clutch 100 is shown schematically, but would operate as known clutchesto not drive the boost compressor 46 through the gear box 200 in thedisconnected position. Alternatively, when connected, it will drive theboost compressor.

The valve 600 is controlled by control 800 in combination with controlof clutch 100. The clutch 100 is controlled in combination with thevalve 600, such that the valve 600 is open as shown in FIG. 2A, and theclutch 100 is disconnected. Thus, most of the air in the duct 26 willpass to outlet 61, and only a small portion of the air will pass intochannels 48, and to the boost compressor 46. On the other hand, when thevalve 600 is closed, and the clutch 100 is connected, as shown in FIG.2B, the majority of the air will flow into the channels 48, and acrossthe boost compressor 46, and little or no air will pass to the outlet61.

The gear box 200 provides an increase of speed at the boost compressor46 or a decrease of speed. Either speed change would provide thedesigner of the gas turbine engine additional control over desired flow,pressure ratio, and packaging size.

While the gear box 200 and clutch 100 are shown acting in combination inthe FIGS. 2A and 2B, either can be used independently of the other inalternative embodiments.

FIG. 3 shows an embodiment 900, wherein the air delivered through achannel 908 to a boost compressor 910 is from a single bypass duct 904.That is, there is only one duct that receives air not directed into thecompressor. A single stage fan 902 delivers air into the bypass duct904, and further into a core engine 906, which includes a compressor, acombustor, and a turbine section, and the turbine section drives theboost compressor 910. For purposes of interpreting the claim, in thisembodiment, the bypass duct 902 would be a low pressure duct.

FIG. 4 shows a variable exhaust cone 242 having an actuator 243 shownschematically, such that the cross-sectional area of an outlet 244 canbe varied. This can provide additional control over the discharge of airdownstream of the boost compressor 46. This variable exhaust cone 242can be utilized to resist or facilitate flow across the boost compressor46, such that the volume of air passing across the boost compressor 46,compared to the volume of air passing to the outlet 61 can becontrolled.

Although an embodiment of this invention has been disclosed, a worker ofordinary skill in this art would recognize that certain modificationswould come within the scope of this disclosure. For that reason, thefollowing claims should be studied to determine the true scope andcontent of this disclosure.

The invention claimed is:
 1. A gas turbine engine comprising: a fanrotor delivering a first portion of air into a low pressure duct, and asecond portion of air into a compressor, said compressor being driven bya turbine rotor, said fan rotor being driven by a fan drive turbine, andsaid second portion of air forming a core air flow passing through saidcompressor, said turbine rotor, and said fan drive turbine; a channelselectively communicating a first part of said first portion of air fromsaid low pressure duct across a boost compressor; and wherein the fanrotor includes at least two stages, with an upstream fan stage of the atleast two stages delivering said first portion of air into said lowpressure duct and a third portion of air across a downstream fan stageof the at least two stages, said third portion of air passed downstreamof said downstream fan stage being delivered as said second portion ofair into said compressor and as a fourth portion of air into a bypassduct; the first part of the first portion of air in said channel passingradially inwardly from said low pressure duct to be radially inward ofthe core air flow downstream of said fan drive turbine, and the firstpart of the first portion of air downstream of the boost compressorpassing outwardly to mix into said core air flow downstream of said fandrive turbine.
 2. The gas turbine engine as set forth in claim 1,wherein said at least two stages of said fan rotor is at least threestages, with a first stage fan of the at least three stages being saidupstream fan stage, and a third stage fan of said at least three fanstages being said downstream fan stage, and there being a second stagefan of said at least three fan stages intermediate said first stage fanand said third stage fan.
 3. The gas turbine engine as set forth inclaim 1, wherein the first part of the first portion of air downstreamof said boost compressor is split into a cooling portion utilized ascooling air, and an exhaust portion exiting into the core air flow. 4.The gas turbine engine as set forth in claim 1, wherein an augmentorsection is positioned adjacent an exhaust nozzle of the gas turbineengine and the first part of the first portion of air downstream fromsaid boost compressor is directed towards said augmentor section.
 5. Thegas turbine engine as set forth in claim 1, wherein an exit conepositioned downstream of said boost compressor is moveable to change adownstream flow cross-sectional area for said boost compressor.
 6. Thegas turbine engine as set forth in claim 1, wherein only the first partof the first portion of air in the low pressure duct is communicatedinto the channel, with the remainder of the first portion of air in thelow pressure duct passing downstream within the low pressure duct to anoutlet of the low pressure duct.
 7. A gas turbine engine comprising: afan rotor including at least one stage, with said at least one stagedelivering a first portion of air into a low pressure duct, and a secondportion of air into a compressor, said compressor being driven by aturbine rotor, and said fan rotor being driven by a fan drive turbine; achannel selectively communicating a first part of the first portion ofair from said low pressure duct across a boost compressor; a valveselectively blocks or allows flow through said low pressure duct to anoutlet, and when the valve is blocking flow more of the first portion ofair is moved into said channel and across the boost compressor as thefirst part of the first portion of air; wherein said channel passesradially inward through a turbine exhaust case strut to the boostcompressor; and wherein a clutch selectively connects or disconnectsdrive from said fan drive turbine to said boost compressor.
 8. The gasturbine engine as set forth in claim 7, wherein said boost compressor isdriven by said fan drive turbine.
 9. The gas turbine engine as set forthin claim 8, wherein a gear box is positioned between said fan driveturbine and said boost compressor, with said gear box affecting a speedchange between said fan drive turbine and said boost compressor.
 10. Thegas turbine engine as set forth in claim 9, wherein a connection betweensaid gear box and said boost compressor is a flexible connection. 11.The gas turbine engine as set forth in claim 7, wherein a clutchselectively connects or disconnects drive to said boost compressor. 12.The gas turbine engine as set forth in claim 11, wherein said clutch ismoved to connect drive to said boost compressor when said valve blocksflow through said low pressure duct to said outlet, and said clutchdisconnects drive to said boost compressor when said valve allows flowfrom said low pressure duct to said outlet.
 13. The gas turbine engineas set forth in claim 7, wherein an exhaust cone positioned downstreamof said boost compressor is moveable to change a flow cross-sectionalarea downstream of said boost compressor.
 14. The gas turbine engine asset forth in claim 7, wherein a gear box is positioned between said fandrive turbine and said boost compressor, with said gear box affecting aspeed change between said fan drive turbine and said boost compressor.15. A gas turbine engine comprising: a fan rotor including at least onestage, with said at least one stage delivering a first portion of airinto a low pressure duct, and a second portion of air into a compressor,said compressor being driven by a turbine rotor, and said fan rotorbeing driven by a fan drive turbine; a channel selectively communicatinga first part of the first portion of air from said low pressure ductacross a boost compressor; wherein the first part of the first portionof air downstream of said boost compressor is delivered into an exhaustgas flow downstream of said fan drive turbine; a valve selectivelyblocks or allows flow through said low pressure duct to an outlet, andwhen the valve is blocking flow more of the first portion of air ismoved into said channel and across the boost compressor as the firstpart of the first portion of air; wherein a clutch selectively connectsor disconnects drive to said boost compressor; and wherein said clutchis moved to connect drive to said boost compressor when said valveblocks flow through said low pressure duct to said outlet, and saidclutch disconnects drive to said boost compressor when said valve allowsflow from said low pressure duct to said outlet.
 16. The gas turbineengine as set forth in claim 15, wherein said channel passes through aturbine exhaust case strut.